Each of the principal investigators for projects I-III is a recognized expert in human and non-human primate embryonic stem and germ cells. The Embryonic Stem Cell and Embryonic Germ Cell ("Stem and Germ Cell") Core draws on this combined expertise, thereby providing a central quality assurance and quality control laboratory for all cellular resources generated by the three projects. Three specific aims are proposed for this core in support of the three projects. Aim 1: Establish and maintain core resource of human and non-human primate embryonic stem cells for distribution to each of the projects and the other cores using good laboratory practice culture and frequent monitoring of pluripotency and aneuploidy. Aim 2: Establish and maintain core resource of non-human primate embryonic germ cells for distribution to each of the projects and the other cores using good laboratory practice culture and frequent monitoring of pluripotency and aneuploidy. Aim 3 (Stem Cell Genetic and Epigenetic Resource) Maintain sets of human and nonhuman primate ES and EG cell lines that are well-characterized with respect to their genetic and epigenetic status (whether normal or abnormal) for use in each of the projects and the other cores. The fulfillment of each of the three aims will support the three projects and the other cores in providing for in vitro molecular and cellular analysis, generation of chimeras (in the case of non-human primate ES and EG cells);and analysis of developmental fates, both in vitro and in vivo (the latter in transplantation studies involving animal models). By combining the expertise and resources of the three project leaders this core maximizes the available resources and reduces duplication and overlap.